The preferred embodiment concerns a developer station for a printer or copier with a rotating developer roller to which toner particles can be supplied, which toner particles accumulate on the surface of the developer roller and are subsequently transferable to a further rotating roller or a continuous belt in a transfer zone. The preferred embodiment also concerns a method for this.
In electrographic printers or copiers, image development methods are used that ink electrostatic charge images on surfaces (for example charge images on a photoconductor) across an air gap or in direct contact with toner particles. These toner particles are located on a developer roller that transfers them directly onto a cylindrical photoconductor or a continuous belt, or they are transferred from the developer roller to a further roller or a continuous belt from which the charge image is then inked on the photoconductor as an intermediate image carrier. The toner image present on the intermediate image carrier is then transferred and fixed onto a print medium (for example paper) in the further course of the printing or copying process.
In order to obtain a high-grade print quality, a homogeneous layer structure of the toner particles on the developer roller is to be maintained as an important prerequisite. Small irregularities in the toner layer can already lead to quality loss in the print image, for example color shifts and brightness fluctuations.
The following print documents are referenced as relevant prior art: DE 101 52 892 A1, DE 31 18 995 A1, EP 0 394 228 B1 and WO 89/08285 A.
U.S. Pat. No. 5,234,786 describes a developer station with a smoothing device which smoothes a mixture made up of carrier particles and toner particles. The smoothing device contains a magnetic smoothing element which exerts a pressure on the mixture layer and smoothes this layer. The developer roller stands directly opposite a photoconductor roller as an intermediate image carrier and transfers toner particles onto the surface of the photoconductor roller to ink the latent intermediate image.
U.S. Pat. No. 5,845,183 describes developer stations in which the developer consists exclusively of toner particles and not of a mixture of toner particles and carrier particles. The smoothing device smoothes the layer consisting exclusively of toner particles on developer rollers.